Polycarbonate resin is an engineering plastic having excellent mechanical strength, high heat resistance, transparency, and the like, and accordingly it has been widely used in various fields such as office automation devices, electric/electronic parts, construction materials, and the like. The resin used in LCD (liquid crystal display) back-light parts requires high reflectivity, light stability, color fixation, and the like, and further requires high fluidity as devices such as televisions, monitors, laptops, and the like are becoming slimmer and thinner.
When a polycarbonate resin is used in LCD back-light parts, the resin is generally colored with high whiteness and used in a back-light frame in order to minimize backlight loss. The white pigment for coloring the resin with high whiteness usually includes titanium dioxide (TiO2) having the highest reflectivity in air.
Conventionally a halogen-based flame retardant and an antimony compound or phosphorus compound are added to a resin composition to impart flame retardancy thereto. However, the halogen-based flame retardant can generate a harmful gas during combustion. Representative phosphorous flame retardants include phosphate ester-based flame retardants. These phosphorous flame retardants, however, can cause a “juicing” phenomenon in which the flame retardant migrates to and deposits on the surface of a molded product during a molding process, and the heat resistance of the resin composition can be significantly decreased.
In order to provide high heat resistance and flame retardancy without using a halogen-based flame retardant, a common technique uses a sulfonic acid metal salt. This technique, however, can deteriorate flame retardancy. Further, the resin can decompose at a high temperature when a large amount of titanium dioxide is used for coloring to provide a high whiteness, so that the mechanical properties of the resin composition can also deteriorate.
Japanese Patent Publication No. 1997-012853 discloses a flame retardant resin composition composed of a polycarbonate, titanium dioxide, a polyorganosiloxane-polyalkyl acrylate combined rubber, a halogen-based and phosphate ester-based flame retardant, and a fluorinated polyolefin-based resin, and U.S. Pat. No. 5,837,757 discloses a flame retardant resin composition composed of a polycarbonate, titanium dioxide, a stilbene-bisbenzoxazole derivative, a phosphate ester-based flame retardant, polyorganosiloxane, and a fluorinated polyolefin-based resin. When these compositions are exposed to a light source for the long time, however, the halogen-based and phosphate ester-based flame retardant can accelerate decomposition of the resin composition to generate significant yellowing, which can deteriorate reflectivity.
U.S. Pat. No. 6,664,313 discloses a flame retardant resin composition composed of a polycarbonate, titanium dioxide, silica, polyorganosiloxane, and a fluorinated polyolefin-based resin. However, since silica is used as a flame retardant, the impact strength of the composition can deteriorate, and the appearance of the injection molded product can also deteriorate.